Let's do some math ..  Rounding examples of 7 random hypothetical purchases:
Case	Tag   Price	Sales   Tax %	Raw Total   Incl. Sales Tax	Rounded   to Penny	Rounded   to Nickel	Rounded   to Dime
Purchase #1	$168.71	12.816%	$190.3319	$190.33	$190.35	$190.30
Purchase #2	$57.54	3.396%	$59.4941	$59.49	$59.50	$59.50
Purchase #3	$178.69	6.749%	$190.7498	$190.75	$190.75	$190.70
Purchase #4	$242.54	6.172%	$257.5096	$257.51	$257.50	$257.50
Purchase #5	$216.87	6.290%	$230.5111	$230.51	$230.50	$230.50
Purchase #6	$167.51	9.616%	$183.6178	$183.62	$183.60	$183.60
Purchase #7	$100.99	6.588%	$107.6432	$107.64	$107.65	$107.60
7 purchase totals =	$1,132.85		$1,219.8575	$1,219.85	$1,219.85	$1,219.70